1. Field of the Invention
The present invention concerns new, hydrolysis-resistant polyester amides with a high molecular weight and partially isocyanate-terminated chains, their production and use, in particular for producing shoe reinforcing materials.
2. Description of the Related Art
The production of polyester urethane films, which serve as self-sticking reinforcing materials and are formed through reaction of polyester chains with isocyanates, is known from the EP-0 323 700 A2 (1). The ratio of isocyanate groups to hydroxyl groups is given at 0.75 to 1.1, preferably 0.9. According to example 1, the material is produced as follows:
Polytetramethylene adipate with a hydroxyl value of 40-45 and an acid value of 0.1-0.7 is heated with 0.003% by weight phosphoric acid and is allowed to react with 7.79% by weight of liquid diisocyanate at 85.degree. C. The resulting product is then extruded into a film, is coated on both sides with a cotton fabric and can be used in this way as shoe reinforcing material, in particular as heel and toe cap material. It has the following characteristics: at 60-125.degree. C., the material is not crystalline, soft and moldable (claim 2). The material is white and crystalline after being heated up to 85.degree. C. and allowed to cool for about 12 minutes. The physical properties of this material are not completely known. Chemically, this is a polyester urethane, which by definition is a compound having urethane groups inserted into the polymer chain.
A high-molecular polyhexamethylene adipate and a method for producing it are described in the EP-0 448 079 A2 (2). In contrast to the material and method described in (1), said material has the desired high molecular weight without the addition of isocyanates. Both polymeric materials are used for the same purpose, namely to replace CAPA.TM. or polycaprolacton; see page 3, line 29 ff. The high molecular weight or the high viscosity of at least 300 cPs is realized in (2) in that the molar ratio of diol/acid is within the range of 0.99-1.03 and that a slight excess of diol is used in particular at a molar ratio of 1.001 to 1.01. The production method is a simple polycondensation at temperatures below 223.degree. C., wherein standard catalysts are used for this.
Another high-molecular polytetramethylene and/or polypentamethylene adipate, and possibly also a polyhexamethylene adipate, are described in the EP-0 499 534 A2 (3). The desired high molecular weight should be at least 10,000, which by the way also corresponds to the weight in (2). The subject-matter in (3) is a polymeric hot-melt adhesive which is to replace the polycaprolacton in the same area of use. In reference (3) no isocyanates are used, and the high molecular weight is realized through a slight excess of diol. Otherwise, both methods are nearly identical, except for the respective charge materials.
The EP-0 572 256 A2 (4) discloses the production of biodegradable, high-molecular aliphatic polyesters. In order to stabilize the polyesters, phosphoric acid or phosphoric acid esters are forcibly added. The polyesters are produced from an aliphatic or alicyclic glycol through esterification with an aliphatic dicarboxylic acid. Following the polyester formation, the phosphoric acid compound and the polyfunctional isocyanate compound are added for the cross-linking. In this way, it is achieved that the final product is biodegradable and high-molecular, but at the same time resistant to thermal decomposition. The final product produced in this way is used in the form of films or foams or in molded parts, primarily for the manufacture of vehicles.
The production of polyester amides through random and block polymerization is furthermore known from the Journal of Applied Polymer Science, 1809-1822 (1982) (5), wherein diols, e.g. decanols, are converted together with adipic acid dichloride and a diamine. Approximately equal parts of all components are used.
The above-mentioned polymeric hot-melting adhesives, however, do not yet have the required bifunctional properties for use as a shoe reinforcing material. Such properties include: a high hydrolysis resistance, paired with a good processability, e.g. in the powder coating technology.
The hydrolysis resistance during the period of use is a very important property as these materials are constantly exposed to moisture. Since the material must be processed within a narrow temperature range of 50 to 80.degree. C., its melting and also its mechanical properties in the crystallized state must be correspondingly optimal.
Above all, it was the object of the present invention to develop hydrolysis-resistant hot-melting adhesive systems on a polyester base, which can be used in particular for the production of shoe reinforcing materials, especially materials with a bifunctional use, namely as a hot-melting adhesives for gluing at temperatures of approximately 50 to 80.degree. C. and also as reinforcing materials.